The present invention is generally directed to a test device for monitoring the electrical characteristics of electronic circuits via the circuit connection pins present on a multi-pin chip circuit package. More particularly, the present invention provides a mechanism for accessing both external and internally positioned pins under actual circuit operating conditions. Even more particularly, the present invention is directed to a method and apparatus for monitoring and testing circuit packages employed in large main frame computer systems. However, the present invention is not limited thereto.
In order to fully appreciate the present invention, it is desirable to possess a complete understanding of the context and systems in which such an invention is typically employed. In particular, in the manufacture of large main-frame computer systems, there is a need for the utilization of circuit packages referred to as thermal conduction modules (TCMs). These modules contain a multiplicity of closely packed integrated circuit chips. Because of the power requirements for these chips, which are designed to operate as quickly as possible, water cooling is provided. These modules, some having thousands of pins, are inserted into circuit boards. Clearly because of the number of pins and the pin spacing, pin alignment is an important aspect of the operation. However, once these modules are inserted into their corresponding circuit boards, typically referred to as TCM or Clark boards, access to the voltages present on the pins is very difficult. However, once all of the TCMs are arranged and configured in a machine, it is nonetheless often desirable to be able to test and determine voltages that appear on certain ones of the pins. Additionally, it may also be desirable to inject signals into various pins.
To facilitate probing of the TCM pins, in one design the TCMs are mounted on a swingable and supportable gate frame for access to the pins from the backside of the Clark board. However, design considerations for power requirements and the length of signal lines can limit the utility of frame rotating mechanisms. Additionally, it should be noted that frame rotation procedures for gaining access to the rear pin configurations of Clark boards and alike make access very difficult. It is noted though that this `frame rotation` is not representative of customer shipped machine layout. Furthermore, it can be difficult to determine exactly which one of hundreds or thousands of pins one wishes to probe from the back of the board. Lastly, it should also be appreciated that the rotation of the frame mechanisms on which the TCMs are disposed is a time consuming operation requiring up to approximately seven hours to achieve because of the signal, power and cooling connections to the TCM and Clark board assembly.
Furthermore, it should be noted that the TCMs themselves possess many hundreds of pins which are relatively closely spaced and which must be carefully aligned. Accordingly, the TCMs themselves typically possess alignment structures and are typically disposed in recessed areas, all of which makes access to the pins themselves that much more difficult. Nevertheless during system test procedures, it is very desirable to be able to determine signal levels that appear on various pins. Oftentimes the signal which is desired to be monitored exists on a pin which lies within relatively inaccessible interior portions of the pin array which protrudes from the bottom of the TCM. Thus it becomes very desirable to be able to monitor pins for which it is very difficult to gain physical access.